title: Over-expression of the cell death regulator BAX inhibitor-1 in barley confers reduced or enhanced susceptibility to distinct fungal pathogens.
abstract: BAX inhibitor-1 (BI-1) is a conserved cell death regulator protein that inhibits mammalian BAX-induced cell death in yeast, animals and plants. Additionally, HvBI-1 suppresses defense responses and resistance to the powdery mildew fungus Blumeria graminis f.sp. hordei (Bgh) when over-expressed in single epidermal cells of barley. To test the potential of ectopic expression of BI-1 to influence fungal interactions with crop plants, we produced stable transgenic barley plants expressing a green fluorescing protein (GFP) fusion of HvBI-1 under control of the cauliflower mosaic virus 35S promoter. GFP-HvBI-1 plants were fertile and did not display obvious developmental alterations when compared to wild type parents. GFP-HvBI-1 plants were more resistant to single cell death induced by ballistic delivery of a mammalian proapototic BAX expression construct and more susceptible to biotrophic Bgh. Microscopic observation of the interaction phenotype revealed that enhanced susceptibility, i.e. a higher degree of successful establishment of haustoria in epidermal cells, was associated with a reduced frequency of hypersensitive cell death reactions. In contrast, young seedlings of GFP-HvBI-1 barley were more resistant to Fusarium graminearum than wild type or azygous controls. Hence the effect of GFP-HvBI-1 on the outcome of a particular plant-fungus interaction appeared dependent on the lifestyle of the pathogen.
authors.affiliation: Institute of Phytopathology and Applied Zoology, Justus Liebig University of Giessen, Heinrich-Buff-Ring 26-32, 35392, Giessen, Germany.
authors.forename: Valiollah
authors.initials: V
authors.lastname: Babaeizad
authors.forename: Jafargholi
authors.initials: J
authors.lastname: Imani
authors.forename: Karl-Heinz
authors.initials: KH
authors.lastname: Kogel
authors.forename: Ruth
authors.initials: R
authors.lastname: Eichmann
authors.forename: Ralph
authors.initials: R
authors.lastname: Hückelhoven
mesh_terms: D017209:Apoptosis / Q000235:genetics*; D001203:Ascomycota / Q000502:physiology; D015870:Gene Expression; D049452:Green Fluorescent Proteins / Q000032:analysis; D001467:Hordeum / Q000235:genetics* / Q000382:microbiology / Q000502:physiology; D007113:Immunity, Innate / Q000235:genetics; D010641:Phenotype; D010935:Plant Diseases / Q000235:genetics* / Q000382:microbiology; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D030821:Plants, Genetically Modified / Q000382:microbiology; D011993:Recombinant Fusion Proteins / Q000032:analysis; D036226:Seedlings / Q000235:genetics / Q000382:microbiology / Q000502:physiology
chemical_list: D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins